Chapter 6: Weathering and Soil Formation

The breaking down of rock and other

substances at Earth’s surface is ___.

weathering

The principle stating that the same processes that operate

today also operated in the past is ____.

Uniformitarianism

Which type of weathering causes the mineral

composition of rocks to change?

Chemical Weathering

What are the most important factors in

determining the rate of weathering?

Type of rock & Climate

What can geologists infer from the rounded,

eroded shapes of the Appalachian Mountains?

The mountains have been eroding for millions of

years.

How does ice wedging cause mechanical weathering of

rock?

Freezing & thawing of water

Does weathering occur rapidly or slowly in a hot

and wet climate?

Rapidly

Which agent of mechanical weathering occurs when rock is worn away by the grinding

action of other rock particles?

Abrasion

A rock containing iron becomes soft and crumbly and reddish-

brown in color. Which cause of chemical weathering has taken

place?

Oxygen

Why does permeable rock weather easily?

Permeable rock contains many small, connected airspaces which allows water to pass

through easily.

Why are areas of limestone easily eroded by groundwater?

Water combines with carbon dioxide as it sinks into the

ground, creating carbonic acid, which slowly dissolves the

limestone.

What begins the process of soil formation?

Weathering of bedrock

Soil that is rich in humus has high___________.

Fertility

Soil formation would take place most rapidly with the weathering of ______.

A. granite on a mountain top.B. limestone in a desert.C. granite in a cold, dry climate.D. limestone in a warm, wet climate.

D. limestone in a warm, wet climate.

Why is soil a valuable natural resource?

Soil is important to all living things on land.

What are the two “jobs” of living organisms in soil?

mix the soil & make humus

Earthworms add their wastes to the soil, then they die and decay in the soil. They are contributing to the formation of __________.

Humus

Which of the following would be found in the “B” horizon?

A.clay, minerals, and little humus.B.humus only.C.partly weathered rock.D.topsoil.

A. clay, minerals, and little humus.

Plant growth and animal activity result in which type of weathering?

Mechanical weathering

Define contour plowing.

The practice of plowing fields along curves of a

slope.

A marble statue is left exposed to the weather. Within a few

years, the details on the statue have begun to weather away.

What is the cause?

Carbonic acid in rainwater

In conservation plowing, why do farmers leave dead weeds and

stalks of the previous year’s crop in the ground?

To retain moisture and hold soil in place